Hair geometry is the natural direction of an individual’s hair growth. It determines, among other things, the resting position of the hair (how the hair “sits”), which gives hair appearance its natural look.
Hair grows straight out from the follicle and exits the scalp at an angle. Human hair also collectively grows in a unique geometric pattern as well which is why we have hair geometry.
A hair whorl is located on the back of the head, near the crown. Hair grows from this location in a clockwise or counterclockwise swirling pattern that determines the overall style and direction of a person’s hair. Some people can have multiple whorls, and some people can have whorl’s closer to the front of the head, which causes “cowlicks” (an expression given to a patch of hair that sticks straight up as if licked by a cow). The hair geometry of a scalp can be different from one person to the next but they all are fairly siimilar overall. All hair growth radiates outwards from a central point in the crown whorl, usually in a clockwise rotational pattern. The rotational swirl is tightest at the center of the crown, and the tight spiral loosens as the rotation moves farther away from the whorl.
It is commonly believed that hair whorls and hair geometry are controlled by genetics. The direction of the whorl is thought to be controlled by a gene with two alleles (alleles are genetic variables) – in this case, there is an allele for clockwise growth and an allele for counterclockwise growth. The common theory is that the allele for clockwise growth is primarily dominant, which is why most hair whorls grow in a clockwise direction.
Yes, scalp hair grows in multiple and various directions at the same time. In fact, the rotational pattern is actually caused by hair growing in separate directions. Hair on the left side of the scalp, for example, typically grows in a forward direction towards the anterior region. Hair on the right side of the scalp, however, grows in a backwards direction towards the posterior of the scalp. These opposing directions are what completes the rotational pattern. While the hair itself always grows upward out of the follicle, the collective geometric pattern can also grow upwards or downwards. Hair on the posterior scalp tends to grow down and slightly toward the left. Hair on the top of the scalp will grow forward towards the hairline with a slight deviation to the right.
A 2009 study attempted to find a link between counterclockwise hair whorls and homosexuality. Researchers believed that if they could find a predisposition towards homosexuality and men whose hair whorls were counterclockwise, then perhaps it would provide evidence that homosexuality is a genetically inherited behavioral trait. To conduct the study, researchers took one hundred pictures of heterosexual men and one hundred pictures of homosexual men, and had two impartial judges determine if the hair whorl was clockwise or counterclockwise for each picture (the judges were not informed of the sexuality of each subject before estimating their hair’s geometry). The study found no meaningful significance to suggest that homosexual men had a high rate of counterclockwise hair whorls.